1. Field of the Invention
The present invention relates to lithographic printing operations and, more particularly, to a non-aqueous cleaning system and method for a printing press recirculation system.
2. Description of the Related Art
Offset printing, or lithography, is a printing technique in which the image to be printed is fixed on a generally flat plate. The lithographic process is based on the principle that oil and water do not mix. Using this principle, the offset printing plate is constructed so that the image areas are ink receptive and lipophilic or water repellant and the non-image areas are hydrophilic or water receptive and ink repellant. Fountain solutions, also referred to as dampening solutions, are the agents used in lithography to wet the non-image area of the plate and repel the ink from such non-image areas.
In use, the typical process for applying fountain solution to the printing plate involves recirculating the fountain solution from a reservoir, through pipes or lines, into a pan on the press where it is applied to the plate by means of a roller system. The constant recirculation of the fountain solution after it has contacted the printing plate leads to the build up of ink, paper lint, gum residues, mold and various contaminants in the recirculation system. As the contaminants build up in the recirculation system, the fountain solution performance degrades and eventually needs to be drained from the system and the system cleaned and refilled with fresh fountain solution.
Several products exist in the industry to clean printing press recirculating systems. All of these prior art products are in liquid form. The typical methodology on which these prior art liquid cleaners are premised involves the following process:
1. Draining and flushing the contaminated fountain solution from the recirculating system;
2. Adding water into the recirculating system;
3. Adding the liquid cleaner into the recirculating system;
4. Running the recirculating system to allow the liquid cleaner to circulated through the system;
5. Draining and flushing the cleaning liquid from the recirculating system; and
6. Adding new fountain solution into the recirculating system.
Frequently, the above process must be repeated more than once to adequately clean the recirculating system.
Although somewhat effective for their intended purpose, the prior art liquid cleaning solutions and methodology include several inherent deficiencies. First, the liquid nature of these solutions causes the containers holding such solutions to be heavy and cumbersome, resulting in significant storage, handling and freight costs. Moreover, the liquid nature of these solutions increases the potential of environmental contamination following spillages and exposure to potentially harmful vapors from VOCs during manufacture and use of the solutions.
Second, the current methodology requires that the contaminated fountain solution be drained and flushed from the recirculating system and fresh water added to the recirculating system prior to the application of the liquid cleaner. In today""s age of increased costs, increased competition and reduced margins, businesses today are constantly striving to find new ways to accomplish tasks in a more efficient and more cost effective manner.
Accordingly, there is still a need in the art for a simplified and more efficient and cost effective means to clean a printing press recirculating system. Any such system should (1) reduce the number of steps and, consequently, the time required to clean a printing press recirculating system, (2) reduce the handling, transportation and storage costs associated with prior art liquid cleaners and (3) reduce the potential health and environmental hazards associated with prior art liquid cleaners. The present invention is particularly suited to overcome those problems which remain in the art in a manner not previously known.
The present invention is directed towards a novel, non-aqueous cleaning system and method for a printing press recirculation system. The cleaning system comprises two powdered compositions. The first composition is prepared by dry blending 15-50% by weight of an alkaline cleaning agent, 15-50% by weight of a detergent salt, 15-50% by weight of an emulsifying/wetting agent, 0-30% by weight of a silicone antifoam and 0-10% by weight of a free-flowing silica additive. The second composition is prepared by dry blending 20-40% by weight of an organic acid and 60-80% by weight of a non-foaming detergent/wetting agent. In use, ten (10) to forty (40) grams of the first composition is dissolved in forty-five (45) to two hundred (200) milliliters of water and the resultant solution is poured into the recirculation system for each gallon of contaminated dampening fountain solution and allowed to recirculate for at least thirty (30) minutes. Five (5) to twenty-five (25) grams of the second composition is then dissolved in forty (40) to two hundred (200) milliliters of water, the resultant solution poured into the recirculation system and the recirculation system is run at least an additional ten (10) minutes. The recirculation system is then drained, flushed with clean water and refilled with fresh fountain solution.
It is an object of the present invention to provide a printing press recirculation system cleaning system and method that has all the advantages of the prior art and none of the disadvantages.
It is another object of the present invention to provide a simplified and more efficient and cost effective means to clean a printing press recirculating system.
It is still a further object of the present invention to provide a cleaning system for a printing press recirculation system which reduces the handling, transportation and storage costs associated with liquid cleaners.
It is also an object of the present invention to provide such a system that may be conveniently packaged, shipped and stored in an efficient, economical and environmentally safe manner.
It is yet another object of the present invention to provide such a system that minimizes reduces VOC emissions and the corresponding potential health and environmental hazards associated with liquid cleaners.
It is yet a further object of the present invention to provide a more efficient method of cleaning a printing press recirculation system by reducing the number of steps and, consequently, the time required to clean a printing press recirculation system.
These and other objects and advantages of the present invention will become more readily apparent in the description that follows.
Before explaining the disclosed embodiment of the present invention in detail, it is to be understood that the invention is not limited in its application to the details of the particular arrangement shown since the invention is capable of other embodiments. Also, the terminology used herein is for the purpose of description and not of limitation.
The present invention is directed towards a new and improved non-aqueous cleaning system and method for a printing press recirculation system. The cleaning system comprises two powdered compositions, each composition being applied to the recirculation system in a two-step process. The first composition is prepared by dry blending 15-30% by weight of an alkaline cleaning agent, 15-30% by weight of a detergent salt, 15-30% by weight of an emulsifying/wetting agent, 15-30% by weight of a silicone antifoam and 0-10% by weight of a free-flowing silica additive. The second composition is prepared by dry blending 20-40% by weight of an organic acid and 60-80% by weight of a non-foaming detergent/wetting agent.
The alkaline cleaning agent is structured to remove fountain solution residue and paper contamination. Additionally, the alkaline cleaning agent provides corrosion protection to the system. The alkaline cleaning agent is preferably sodium metasilicate. However, other suitable water-soluble silicate compounds may, alternatively, be employed.
The detergent salt functions to suspend and chelate insoluble metal salts normally found in inks and increase the effectiveness of the alkaline cleaning agent. In the preferred embodiment, the detergent salt is preferably sodium tripolyphosphate, although other alkaline phosphate salts may be used.
The emulsifying/wetting agent removes oily residues in the recirculating systems, such as inks and ink oils. In the preferred embodiment, the emulsifying/wetting agent is of the alkyaryl-type, such as that manufactured by Stepan Company under the brand name Nacconnol 90 G, which has high detergency and relatively low foaming characteristics compared with other detergents.
The alkaline cleaning agent, detergent salt and emulsifying/wetting agent are foaming materials. Accordingly, the antifoam is used to prevent the formation of foam, which may result in overflow, and to facilitate removal and flushing of the contaminated fountain solution. In the preferred embodiment, the anti-foaming agent is of a silicone-type, such as that manufactured by Dow Chemical Company under the name Q2-3183. The defoaming capabilities of this particular agent is superior to other anti-foaming agents due to its hydrophobic silica content and its stability in the alkaline medium of this composition.
The silica additive functions to make the mixture a free-flowing powder, which prevents clumping and allows for easy dissolution. The silica additive is preferably of the type manufactured by Degussa Corporation under the brand name Sipernat 50 S, due to its ability to accommodate a high moisture load and still maintain its free-flow properties. However, other suitable silica additives may, alternatively, be used.
The organic acid used in the second composition functions to re-acidify the cleaning agents of the first composition after the first composition has been circulated through and cleaned the recirculation system, thereby preventing cleaner residue from contaminating the replacement fountain solution added to the recirculation system after the old, contaminated fountain solution is drained and the system flushed. This is necessary because the pH of the fountain solution, which is typically between 3.5 and 5.5, rises to approximately 12 after the first composition is added. Thus, the second composition acts to lower the pH back to the 3.5 to 5.5 range. In the preferred embodiment, malic acid is the organic acid because of its low tendency to form insoluble metal precipitates in the solution being cleaned. However, any suitable powdered, non-corrosive acid may, alternatively, be employed.
The non-foaming detergent/wetting agent of the second composition acts as an added cleaner, facilitating removal of loosened debris during flushing. The preferred detergent/wetting agent is sodium xylene sulfonate because it is non-foaming and has minimal effect on the pH of the acidifying solution. Other non-foaming alkylaryl sulfonates may, alternatively, be used.
In use, ten (10) to forty (40) grams of the first composition is dissolved forty-five (45) to two hundred (200) milliliters of water and the resultant solution is poured into the printing press recirculating tank for each gallon of contaminated dampening fountain solution. The resultant mixture is then allowed to recirculate for at least thirty (30) minutes (Step 1).
Five (5) to twenty-five (25) grams of the second composition is then dissolved in forty (40) to two hundred (200) milliliters of water and the resultant solution poured into the recirculating tank. The recirculation system is then run for at least an additional ten (10) minutes (Step 2). The recirculation system is then drained, flushed with clean water and the tank refilled with fresh fountain solution.
It should be appreciated that the composition of the present invention may be embodied in a wide range of operable formulations as illustrated by the examples below. The composition may be provided in solid or powder form and is structured to be dissolved in water prior to being added to the recirculation system sump tank. Although pre-dissolving the powder or solid in water attains a greater degree of accuracy, the powder could, alternatively, be added directly to the sump tank. Each of the compositions disclosed in the following examples were formulated in a free-flowing powder form.